Weld distribution for shadow mask to frame assembly

ABSTRACT

An aperture mask-frame assembly for use in a color cathode ray tube wherein the foraminous portion is affixed to its supporting frame in a manner to provide the mask with floating corner sectors which are structurally strengthened by a pair of cooperating supporting welds discretely spaced on either side thereof to enhance thermal equilibrium between the mask and the frame and markedly improve the structural strength of each corner sector by inhibiting pivotal movement of the sector mask material about the terminal points of affixation.

United States Patent Appl. No.

George R. Kautz Seneca Falls, N.Y.

Feb. 3, 1969 Jan. 5, 1970 Sylvanh Electric Products Inc. a corporation of Delaware inventor Filed Patented Assignee WELD DISTRIBUTION FOR SHADOW MASK TO FRAME ASSEMBLY 2 Claims, 4 Drawing Figs.

US. 313/85, 29/25. 1 5 Int. l-l0lj 29/02 Field of Search 313/928, 858

[ 56] References Cited UNITED STATES PATENTS 3,368,098 2/1968 Demmy 313/858 Primary Examiner- Robert Segal Attorneys-Norman J. OMalley, Cyril A. Krenzer and Frederick H. Rinn ABSTRACT: An aperture mask-frame assembly for use in a color cathode ray tube wherein the foraminous portion is affixed to its supporting frame in a manner to provide the mask with floating corner sectors which are structurally strengthened by a pair of cooperating supporting welds discretely spaced on either side thereof to enhance thermal equilibrium between the mask and the frame and markedly improve the structural strength of each comer sector by inhibiting pivotal movement of the sector mask material about the terminal points of afiixation.

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' ATTORNEY i WELD DISTRIBUTION FOR SHADOW MASK T FRAME ASSEMBLY BACKGROUND OF THEINVENTION This invention relates to color cathode ray tubes of' the aperture mask type and more particularly to the mask-frame assembly and means of affixing the mask portion to the supporting frame.

In one of the conventional types of .multibeam cathode ray tubes a domed metallic aperture mask is suitably supported within the envelope in spaced relationship to an adjacent 1' cathodoluminescent screen formed on theinner surface of the tube face panel. A common type of patterned screen'utilized I with the above-mentioned mask may be comprised of a multitude of dot triads of different color emitting phosphors disposed on the panel in a predetermined sequence in related registry with the apertures in the foraminous mask. The aligninent relationship of the mask apertures with the dots of the screen pattern is a requisite for subsequent phosphor excitation by specific electron beams directed thereto.

As the domed foraminous mask portion is of thin gauge material, it is readily heated by electron bombardment during the early period of tube operation. Upon heating, the center portion of the mask reaches thermal equilibrium before the peripheral portion thereof; thereby producing a resultant ex- .pansive radial movement of the mask material which moves .the apertures and thereby shifts the beam landings on the dots. With continued operation of the tube, the temperature of the 'mask supporting frame is elevated by both electron impinge- .ment and heat conduction from the mask. The resultant ex- 'pansion results in moving the apertures and the beamlandings 'in a reverse order whereby the final beam landings in the operating tube are not always oriented in desired relationship on the dots of the screen pattern.

It was found that disposing a series of welds completely around the periphery of the rectangular mask-frame assembly restricted the expansive movement of the mask during early tube operation causing distortions therein. This was especially noticeable in the formed corner regions of the mask, which because of their shape, were exceptionally rigid when welded to the frame. To alleviate the rigid relationship between the mask and the frame, fewer welds were employed in addition to removing welds from the corner regions of the assembly. The use of fewer spaced apart points of affixation permitted the thin mask material to more readily effect a hinge action at the points whereat it was bonded to the frame, but the unbonded or floating corner regions were noticeably structurally weaker.

During the formation of the patterned screen, there is need to several times insert and remove the mask from the panel. During these times, the mask is vulnerable to distortion. It was found that, when the floating corner regions of the mask were inadvertently subjected to slight handling pressures, the

formed comer sectors tended to readily pivot on the end welds structural deficiency, by tacking each comer with a single vertex oriented weld, promoted corner rigidity, but defeated the intended expansion advantage of the floating corner structure of the assembly.

. Additionally, it was noted that an absence of welding bonds between the mask and the frame 'in the floating corners reduced the heat conduction therebetween thereby contributing to a time delay in reaching thermal equilibrium in those portions of the mask.

OBJECTS AND SUMMARY OF THE INVENTION It is an object of the invention to reduce the aforementioned disadvantages and to provide a bonded mask-frame assembly wherein the floating corner sectors have improved structural strength. Another object is to enhance thermal equilibrium of thefloating corner regions.

The foregoing objects are achieved in one aspectof the invention by disposing a pair of discretely spaced bonds, referenced respectively as terminal and guard welds, on either side of each comer sector. Each pair of such welds is oriented in a predetermined manner relative to and spaced from centrally established x and y axes in the assembly. The terminal weld of each pair constitutes a terminal point of mask affixation relative to each side of the sector. The spacing between the terminal and guard welds of each. pair, being within the range of 0.375 to 0.750 inch, is less than the spacing between the guard weld and the next mask-frame affixation weld disposed along the respective framing portion. Each pair of sector related welds promotes enhanced thermal equilibrium between the mask and the frame by providing additional closely related conduction means, and markedly improves the structural strength of each floating corner sector by inhibiting pivotal movement of the sector mask material about said terminal points of affixation.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view illustrating basic features of one type of color cathode ray tube wherein a mask-frame assembly is utilized;

FIG. 2 is a plan view of a mask-frame assembly from a tube such as that shown in FIG. 1; and

FIGS. 3 and 4 are elevational views of the mask-frame as sembly taken along the lines 33 and 44 of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT For a better understanding of the present invention, together with other and further objects, advantages and capabilities thereof, reference is made to the following disclosure and appended claims in connection with the above-described drawings.

With reference to the drawings, there is shown in FIG. .1, a cathode ray tube 11 having an envelope 12 comprising a neck portion 13, a funnel portion 15, and a panel portion 17, with a longitudinal axis 19 extending therethrrough. Within the neck portion there is positioned a source of electrons 21 which projects one or more electron beams 23 toward a domed foraminous mask 25 affixed to a suitably formed supporting frame 27. The mask-frame assembly 29, comprising the aforementioned mask and frame, is spacially superposed, by means not shown, relative to a patterned cathodoluminescent screen 31 disposed on the interior surface 18 of the panel 17.. The representative electron beam 23 passes through the apertures 26 in the foraminous mask in a predetermined manner to impinge and excite one or more of the dots in the tridot arrays of green, red and blue electron responsive phosphors comprising the patterned screen therebeneath. Means for supporting'the mask-frame assembly within the panel are not shown as they are not considered pertinent to the invention.

In greater detail and with reference to the several figures, there is shown a substantially rectangular mask-frame assembly 29. The metallic frame 27 is a continuous supporting member having an instanding peripheral ledge 33 and an 'upstanding sidewall 35 which has a terminal contour 36 formed in relationship to the contour of the panel surface 18 adjacent thereto. The continuous supporting member is a formedintegration of framing elements comprising a combination of top, bottom, and side elements, respectively.

. and domed to have a curvature related! to that of the panel sur face 18 being spaced therefrom by the predetermined distance d. A perimetric rim 51 is formed to provide substantially contiguous capping engagement with the terminal contour 36 of the framing member 27. Positioning of the formed mask portion on the supporting frame provides an unbonded preassembly wherein the mask portion is suitably adjusted on the frame, by means not shown, in a manner so that the mask of the completed assembly will have the desired distance d relationship with the interior surface 18 of the panel in the finished tube. With the mask and frame portions so positionally interrelated, a plurality of affixation bonds or welds are discretely and spacedly disposed along the perimetric rim to provide a mask-frame assembly wherein subsequent hinged movement of the mask is facilitated during the initial thermal expansion of the mask portion during tube operation. The integral mask-frame assembly 29 has an assembly axis which is substantially coincidental with the tube axis 19 and definitive structural perimetric regions such as a top portion 37, a bottom portion 37' and side portions 39, 39' respectively, with four transitional corner sectors 41, 42, 43, and 44, each defining a respective comer vertex 45, 46, 47, and 48. defining The mask to frame welds are disposed in a manner removed from the assembly corners to provide weld-free floating comer sectors. The welds proximal to each corner sector are in the form of a pair of two spaced apart welds discretely positioned on either side thereof to enhance thermal equilibrium between the mask and the frame and to provide structural strength to each floating corner sector by inhibiting pivotal movement of the sector mask material about the terminal points of affixation. Each pair of sector-related welds are disposed in a predetermined manner at locations around the perimeter of the assembly relative to and spaced from common x and y axes, designated by intersecting lines x,x' and y,y', having their point of origin on the mask axis C oriented in a plane substantially normal to that axis. The x and y axes are established to substantially bisect the assembly being extended thereacross in a manner to substantially bisect the top, bottom and side portions respectively to divide said assembly into four conventional quadrants. These are delineated in a counterclockwise manner wherein Quadrant 1 includes that portion of the mask-frame assembly included within the axes designation X-C-y, Quadrant II by x-Cy, Quadrant III by x'-C-y, and Quadrant IV by X -C-y, respectively. To expedite clarity in the specification, deposition of exemplary sector-related pairs of welds will be described with reference to the above-noted Quadrants l and N.

For example, in Quadrant 1, corner sector 41 has related points of affixation in the form of two pairs of spaced apart welds, 55 and 57 disposed on either side thereof. Each of the above-noted pairs has a terminal weld 59, 61, and an associated guard weld 63, 65. The terminal weld of each pair constitutes a terminal point of mask afiixation relative to each side of the sector to provide a weld-free floating corner sector therebetween. Because of its form, the comer sector has restricted flexibility, therefore it is advantageous, from the standpoint of reducing mask distortion due to thermal expansion, to maintain each corner sector as a floating structure. To provide this type of floating corner sector having the desired rigidity, it is important that the terminal points of aflixation be properly oriented.

To locate the terminal welds 59, 61, of the respective pairs it is expedient to first define the corner vertex 45 with reference to the common x and y axes by utilizing abscissas and ordinates associated therewith. The vertex of the comer sector 41 is defined substantially an abscissa value of YT and an ordinate value of xw. The top terminal weld 59 in Quadrant l on the perimetric rim of the top portion 37 of the assembly is substantially determined by an abscissa value of YV and an ordinate value of xv. It has been advantageous to orient top terminal weld 59 within a location range of 50 to 65 percent of the distance from the vertical assembly bisecting line or axis to the top corner vertex 45 defined by the H abscissa determinant, i.e. the value of:

A in similar manner, the side terminal weld 61 of pair 57 in Quadrant l is determined on the perimetric rim of the side portion 39' by an abscissa value of z and an ordinate value of xz. It is advantageous to orient this side terminal weld within a location range of 50 to 65 percent of the distance from the horizontal assembly bisecting line or x-x' axis to the top corner vertex defined by the w-w' ordinate determinate, i.e. the value of:

In general, for both the top and side terminal welds, the higher percent portion of the location range applies primarily to larger size mask-frame assemblies and the lower percent portion to smaller sizes thereof.

The locations of the respective top and side guard welds 63, 65 associated with the top and side terminal welds 59, 61 are highly important as the discrete locations of the respective guard welds determine the strengthening pivot-inhibiting feature of the invention. With particular reference to Quadrants l and IV, it has been found that the guard welds 63, 63' should be separated from their respective terminal welds 59, 59 by a spacing m substantially within the range of 0.375 to 0.750 of an inch. Spacing within this range provides improved structural strength to the corner sector in a manner to prevent proximal buckling of the rim and adjacent mask material thereby inhibiting pivotal movement of the sector mask material. Thus, a more rugged assembly is effected. This spacing relationship holds true for all eight pairs of corner sector related welds disposed in all four Quadrants of the assembly. The described pairs of welds also provide improved heat conduction between the mask and the frame to enhance the thermal equilibrium of the floating comer sectors by reducing the time required for normal expansive response of the formed material in those regions.

The above noted spacing range m between the terminal and guard welds of each pair is less than the adjacent spacing n between the guard weld of each pair and the next mask-frame affixation weld 69, 69 disposed along the respective perimetric portion of the assembly to facilitate the aforementioned desired hinging effect of the mask portion. This spacing relationship between the guard welds and the next weld of affixation adjacent thereto applies to all of the eight guard welds in the four Quadrants of the assembly. In some instances, especially in small size mask-frame assemblies the next weld of affixation may be the guard weld of another corner sector related pair of welds associated with another corner of the assembly.

In any one assembly structure, the opposed terminal welds of the top and bottom portions and the two side portions are at locations having abscissas and ordinates of substantially similar values.

Thus, there is provided a bonded rectangular aperture mask-frame assembly wherein the four floating corner sectors thereof exhibit improved structural strength and wherein the thermal equilibrium characteristics of the respective corner regions are likewise improved.

While there have been shown and described what are at present considered the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention as defined by the appended claims.

lclaim:

1. In a color cathode ray tube having an envelope with a longitudinal axis extending therethrough and a patterned cathodoluminescent screen disposed on the face panel thereof with at least one electron gun oriented therein to beam electrons to said screen, a substantially rectangular aperture maskframe assembly positioned therein intermediate said screen and said electron source comprising: a metallic frame in the form of a continuous supporting member panel surface adjacent thereto, said continuous member being a formed integration of top, bottom and side elements having transitional comers therebetween; and a foraminous mask portion perimetrically shaped to be compatible with said frame and having a domed curvature related to that of said panel surface with a perimetric rim formed in a manner to provide substantially contiguous capping engagement with the contoured terminal portion of said integrated framing member to constitute a mask-frame assembly having an assembly axes substantially coincidental with said tube axis, said assembly having top, bottom and side perimetric portions with four formed transitional comer sectors therebetween wherein a respective comer vertex is substantially defined, said mask portion being affixed to the frame supporting member by a plurality of spaced-apart welds disposed on the perimetric rim of the mask substantially removed from said corners to provide weld-free floating comer sectors, the points of afflxation proximal to each comer sector being in the form of a. pair of two spaced-apart welds referenced respectively as terminal and guard welds disposed on either side of the sector whereof the terminal weld of each pair constitutes a terminal point of mask affixation relative to each side of the sector, the spacing between said terminal and guard welds of each pair being to thereby enhance thermal equilibrium between the mask and the frame and to provide structural strength to each corner sector by inhibiting pivotal movement of the sector mask material about Attesting Officer 222 5 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Pacenc'No. 3,553,516 Dated January 5, 1971 Inventor(s) George R. Kautz It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 4, line 5, of the specification, "A in similar" shoul read--In similar--.

Column 4, line 7 "2" should read--yz--.

Column 5, line 4 of Claim 1, the followin mline was left oui and should be inserted between the words ember" and "paneI --terminally contoured in relationship to the contour of th1 Column 6, line 9, of Claim 1, the following line was left 01 and should be inserted between the words "being" and "to"--v substantially within the range of 0.375 to 0.750 of an inch Signed and sealed this 11th day of May 1971 (SEAL) Attest:

EDWARD M.FLETCI'IER,JR. WILLIAM E. SGHUYLER, J

Commissioner of Patent 

1. In a color cathode ray tube having an envelope with a longitudinal axis extending therethrough and a patterned cathodoluminescent screen disposed on the face panel thereof with at least one electron gun oriented therein to beam electrons to said screen, a substantially rectangular aperture mask-frame assembly positioned therein intermediate said screen and said electron source comprising: a metallic frame in the form of a continuous supporting member panel surface adjacent thereto, said continuous member being a formed integration of top, bottom and side elements having transitional corners therebetween; and a foraminous mask portion perimetrically shaped to be compatible with said frame and having a domed curvature related to that of said panel surface with a perimetric rim formed in a manner to provide substantially contiguous capping engagement with the contoured terminal portion of said integrated framing member to constitute a mask-frame assembly having an assembly axes substantially coincidental with said tube axis, said assembly having top, bottom and side perimetric portions with four formed transitional corner sectors therebetween wherein a respective corner vertex is substantially defined, said mask portion being affixed to the frame supporting member by a plurality of spacedapart welds disposed on the perimetric rim of the mask substantially removed from said corners to provide weld-free floating corner sectors, the points of affixation proximal to each corner sector being in the form of a pair of two spacedapart welds referenced respectively as terminal and guard welds disposed on either side of the sector whereof the terminal weld of each pair constitutes a terminal point of mask affixation relative to each side of the sector, the spacing between said terminal and guard welds of each pair being to thereby enhance thermal equilibrium between the mask and the frame and to provide structural strength to each corner sector by inhibiting pivotal movement of the sector mask material about said terminal points of affixation.
 2. The aperture mask-frame assembly according to claim 1 wherein said opposed terminal welds of the respective pairs of welds have abscissas and ordinates of substantially similar values. 